This invention relates to an image forming apparatus that is capable of image formation not only from reflection-type originals such as printed matter and photographic documents but also from transmission-type originals such as lantern slides and proofs. The apparatus allows image of high quality to be formed from various kinds of documents by simple steps of operation whether they are of a reflection or transmission type.
Most of the conventional image forming apparatuses such as color copiers and various types of color printers have been adapted for reproducing image from reflection-type originals such as printed matter. However, the technology of recording image information has recently become so versatile that image forming apparatuses have been commercialized that are capable of image recording on light-sensitive materials by reading image not only from reflection-type originals such as printed matter and photographs but also from transmission type originals such as lantern slides, proofs and microfilms.
Image forming apparatus that is adapted for the use of both a reflection-type and a transmission-type original is equipped with a light source unit on a scanning unit that compose the exposure optics for image formation from the transmission-type original, and the user performs imagewise exposure on the light-sensitive material by means of the appropriate exposure optics as selected in accordance with the kind of document to be duplicated and the size of the transmission-type original of interest.
The image forming apparatus of this dual type performs imagewise exposure on an ordinary reflection-type original by means of exposure optics that is inherent in the apparatus and which comprises in combination a linear scanning head for issuing illuminating light, a plurality of mirrors, light modifying color filters and diaphragm, imaging lenses, etc.
To perform imagewise exposure with exposure optics inherent in the image forming apparatus (which optics in hereunder referred to as "inherent exposure optics"), the linear scanning head is moved in a direction generally perpendicular to its length so that the reflection-type original placed on the document platen is scanned two-dimensionally with the illuminating light from the head. Slit light reflected from the original is guided by the plurality of mirrors to travel in a predetermined optical path and, after being adjusted for its colors and quantity by means of the color filters and diaphragm and for the imaging position, magnification, etc. by means of the imaging lens, the light is admitted and focused at the position of imagewise exposure on the light-sensitive material that is moving in synchronism with the scanning head, thereby completing the process of exposure of the light-sensitive material.
For image formation from comparatively large transmission-type originals such as 4(in).times.5(in) size lantern slides and proofs, it is known to use a dedicated light source unit that illuminates from above the transmission-type original placed on the document platen (or held in its neighborhood).
When using this light source unit, the image of the transmission type original is also read by means of the aforementioned inherent exposure optics; the light from the light source unit that has passed through the original is scanned without tuning on the light source in the scanning head and, as in the manner described in connection with image formation from the reflection-type original, the transmitted light is focused at the position of imagewise exposure on the light-sensitive material, thereby completing the process of exposure of the light-sensitive material.
In addition, for image formation from small-size transmission type originals such as 135 size lantern slides, it is known to use a film scanning unit having exposure optics of a projection type as disclosed in Japanese Patent Application (kokai) No. 2(1990)-242246. Being designed for use as an attachment to a predetermined part of the image forming apparatus, this film scanning unit of the projection type comprises such basic components as a projecting light source, light modifying color filters, a ND filter for adjusting the quantity of light a document holder that moves (for scanning) as it carries the transmission-type original, a slit defining member that restricts the light transmitted through the original, a zoom lens for image enlargement, and mirrors for adjusting the optical path.
The process of image formation from the transmission-type original by means of the film scanning unit proceeds as follows. Light issuing from the projecting light source that has its colors and quantity adjusted by the color filters and ND filter is allowed to be incident on the original on the document holder and the transmitted light is shaped by the slit-defining member to form elongated slit light. The document holder moves in a direction corresponding to the movement of the scanning head (in the direction of transport of the light-sensitive material) in the image forming apparatus and the slit is elongated in a direction generally perpendicular to the movement of the holder; consequently, the transmission-type original is subjected to slit scanning.
The transmitted light coming out of the slit is admitted into the zoom lens which performs image enlargement at a preset magnification and its optical path is brought into registry with that of reflected light from the reflection-type original (see the foregoing discussion) by means of the mirrors that can be inserted into or removed from the optical path in the inherent exposure optics; subsequently, as in the case of image formation from the reflection-type original, the transmitted light is incident and focused on the light-sensitive material moving in synchronism with the movement of the transmission-type original (and the document holder, too), thereby completing the process of exposure of the light-sensitive material.
A problem with these conventional image forming apparatuses such as a color copier and a color printer is that the exposure optics and the mechanism for transporting the light-sensitive and image-receiving materials can experience mechanical deviations or that the light-sensitive material and even the developing material may be subject to variations from one production lot to another, as well as time-dependent changes and deterioration and that, therefore, it is difficult to insure that image faithful to the image of the color original can always be reproduced.
Even if the same model of image forming apparatus is used and operated under the same image forming conditions with a view to forming the same image, the above-described mechanical factor, lot-to-lot variation, time-dependent changes and deterioration will affect the reproduction of image to upset the color balance or afford different densities.
Therefore, in order to insure that the conventional image forming apparatus will always form image that is faithful to the image of the original in terms of color and density, the appropriate image forming conditions, or the conditions for color balance and density that can reproduce a faithful image, must not only be set at the time when the image forming apparatus is installed or when the light-sensitive material or the image-receiving material, as well as the developing material are replaced but also be reset periodically after the installation of the apparatus.
The conventional color image forming apparatus is so adapted that the color balance, color shades, density and other factors of the image to be formed are adjusted manually in accordance with various parameters including the user's preference, the intended use of the formed image, and the state of the image of the original.
However, in the conventional color image forming apparatus that is designed to duplicate image from both a reflection-type and a transmission-type original, not only the method of setting or resetting the image forming conditions but also the method of adjusting the image color and/or density manually (which is hereunder referred to as "color/density adjustment") varies, with the exposure optics or unit to be employed, namely, with the kind of document to be duplicated, and the user has found the steps of operation for setting the image forming conditions or performing color/density adjustment to be not only extremely inefficient but also cumbersome and difficult to perform.
When duplicating image from color reflection-type original on the conventional image forming apparatus, the image forming conditions are typically set in the following manner: the intended image is actually formed using predetermined reference charts and, with the formed image being visually inspected or electronically read with a sensor or the like, the operating panel on the image forming apparatus is touched to adjust the amount of insertion of various color [i.e., cyan (C), magenta (M) and yellow (Y)] filters fitted in the inherent exposure optics, as well as the amount of control by the diaphragm and the so adjusted values are entered into the apparatus for storage as data.
Image formation is also accomplished by means of a light source unit using a sleeve or the like. In this case, inherent exposure optics is also used but, on the other hand, it is impossible to preset the conditions for image formation from a transmission-type original. To form image of high quality, the user must check the actually formed image and repeat the routine for another image formation by touching the operating panel inherent in the apparatus to make the necessary adjustments of colors, densities, etc.
When a film scanning unit is used to perform image formation from a small-size transmission-type original such as a lantern slide, the necessary image forming conditions are preset by means of the color (C, M and Y) filters and the ND filter for adjusting the intensity of light, all of which filters are fitted in the film scanning unit; however, in practice, in order to adjust or preset the image forming conditions using those filters, the operating means on the film scanning unit must be touched in an operational manner entirely different from the one used in image formation from a reflection-type original or a large-size transmission-type original.
This is also true in the case of performing color/density adjustment in accordance with the intended use of the formed image or the state of document to be duplicated; when forming image from a reflection-type original or a large-size transmission-type original, the necessary adjustment is accomplished by the operating panel inherent in the apparatus whereas the adjusting means fitted in the film scanning unit is used to achieve the adjustment of interest for a small-size transmission-type original such as a lantern slide.
In short, the conventional image forming apparatuses require entirely different methods of operation for adjusting the image forming conditions or making the necessary color/density adjustments for image formation depending not only upon the kind and size of the document to be duplicated but also upon the exposure optics to be selected accordingly, and this has presented the user with a serious problem in that he finds the steps of operation for the image forming process extremely cumbersome and difficult to perform.